There are available to the consumer an ever-increasing number of portable battery operated devices. Those devices create an ever-increasing demand for batteries to serve as power sources. Conventionally, primary batteries such as carbon-zinc or alkaline batteries have been used as power sources, but since these primary batteries are typically not designed for recharging, the consumer is forced to continually replace the used-up primary batteries with new fresh batteries.
Nickel-cadmium batteries are available which can repeatedly be recharged and reused for a significant number of charge/discharge cycles. Such nickel cadmium batteries are often made with a terminal and case configuration identical to that of primary batteries so as to be useable in the relatively large number of products designed to use primary batteries. These nickel cadmium batteries are usually associated with battery chargers for charging of the batteries. However, providing chargers for such nickel cadmium batteries creates the opportunity for insertion of primary batteries, having the same size and shape configuration, into the charger by an unwary consumer, even though such primary batteries are not intended to be recharged. It has been found that many carbon-zinc and alkaline batteries, if subject to charging current, will eventually release electrolyte which can corrode and damage the product into which the battery is inserted. Charging of such primary batteries may also produce other adverse effects.
In prior art approaches, in order to provide for charging of nickel-cadmium batteries while avoiding the adverse effects associated with recharging primary batteries, the nickel-cadmium batteries have been made of special size or shape to distinguish them from the non-rechargeble or primary batteries so that only the rechargeable battery will physically fit into a charger for recharging. Other prior art approaches have provided the rechargeable battery with a third contact terminal (in addition to the two contact terminals used to discharge energy from the battery) which is used to charge the battery. A non-rechargeable battery not having the third charging contact terminal cannot be charged in the charger. Another prior art approach provides for the insertion of a uni-directional current flow device into the non-rechargeable battery so that current may flow from the battery during discharge but cannot flow through the battery in the reverse direction during charging. Each of these prior art approaches has not proved to be entirely satisfactory at least for the reason that they each involve additional or special parts or components and hence increase the cost of the battery.
In view of the foregoing, it is the general purpose of the present invention to provide a rechargeable battery system including a special battery and battery charger which avoids the possibility of providing recharging current to a non-rechargeable battery. More particularly, it is an object of the invention to provide a special rechargeable battery and a battery charging system which cooperate for recharging of the special batteries by enabling the charger to deliver charge current when a special rechargeable battery is inserted therein but which prevent the charger from delivering charge current if another battery is inserted.
In practicing one aspect of the present invention, it is an object to provide a battery charging system for charging multiple batteries in which each battery is provided with an indicia indicating such battery is of the rechargeable type, and the charging system is not enabled unless each battery inserted is of the special rechargable type.
Another object of the present invention is to provide a battery system as characterized above that makes it exceedingly difficult for the consumer to override the feature of the charger which prevents charging of the primary batteries by such tactics as inserting conductive elements, for example metallic foil or the like, in the charger to bridge electrical sensing contacts.